(1) Field of the Invention
This invention relates to a process for isomerizing a glucose-containing solution to convert at least a part of the glucose to fructose.
(2) Description of the Prior Art
Glucose isomerase is an enzyme capable of converting glucose into fructose and vice versa and is used for producing fructose from glucose.
Many proposals have been made to stabilize and/or to immobilize glucose isomerase for the multiple reuse thereof. For example, U.S. Pat. Nos. 3,708,397 and 3,788,945 teach the immobilization of glucose isomerase with DEAE, TEAE or ECTEOLAcellulose. These celluloses are used in the form of a microgranule, fine fiber or a cake. These forms are not convenient to handle. Furthermore, when these celluloses are packed in a column, they tend to be densified during the use, and hence, cause a large pressure loss and prevent the passage of a glucose substrate solution. Japanese Laid-open Patent Application 53,582/1975 discloses the immobilization of glucose isomerase with a macroreticulated or porous anion exchange resin. However, the isomerase immobilized anion exchange resin exhibits an undesirably low enzymatic activity and is also poor in the retention of activity. Japanese Laid-open Patent Applications 1181/1973 and 92,277/1974 teach that a homogenized microorganism cell concentrate containing ruptured cells is treated with glutaraldehyde to form a crosslinked coherent solid product. This crosslinked product is also not satisfactory in its enzymatic activity. Furthermore, once the enzymatic activity of the crosslinked product decreases due to repeated use, it is difficult or even impossible to regenerate its enzymatic activity.